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Novel high spin tri-, tetra-, pentaradicals, composed of triazine coupling units and cationic amino radical spin centers (+ . NH) under various configurations and linkages, are predicted from AM1-CI calculations. It is found that for charged planar multiradicals the stability of high spin ground states depends on both the molecular configuration and the number of end groups. Generally, cyclic 1,3-bridged charged multiradicals (S less than or equal to 5/2) possess more stable high spin ground states than their isomers under the branched 1,3,5,-bridged configuration. Therefore, it is suggested that in the design of planar high spin molecules with stable high spin ground states, less end groups and all the supposed spin centers and/or the coupling units should be under the same structural situation. (C) 1999 Elsevier Science B.V. All rights reserved.

Theoretical studies on structures and properties of endohedral fullerene complexes formed by encapsulating small molecules of HF, H2O, NH3, and CH4 in a C32 fullerene cage, were carried out by ab initio method. Current calculations reveal that these processes to encase them in fullerene are energetically unfavorable because of the small cavity size of C32. The red shift in the F-H stretching frequency indicates the potential existence of hydrogen bonding between the HF molecule and the carbon cage.

With the aim to explore the nature of interaction between organic radicals and paramagnetic ion, unrestricted density functional theory (UDFT) and restricted open shell DFT (RO-DFT) calculations using 6-31G(d) and LANL2DZ basis sets have been performed on the 1:2 complexes of bis(hexafluoroacetylacetonato)copper coordinated with 4-(N-tert-butyl-N-oxyamino)pyridine, complex 1. Structural data revealed by X-ray crystal analysis are used. It is found that the calculated results depend on the selected functionals, model orientation, basis set form and symmetry constraint. The proper chemical models for investigated system are RO-B3LYP, RO-BLYP, RO-PBE, and RO-PBE0.

Poly( p -phenylenevinylene) thin film was prepared by spin-casting onto optically transparent ITO conduction glass substrate, and its photoelectric properties were studied with surface photovoltage spectra. A localized subgap electronic transition is found, which causes the photovoltaic response with polarity opposite to that from band-to-band electronic transition ( π–π *). With the help of the photovoltaic properties under the external electric field, this localized transition is assigned to a electronic transition from the valence band to a local state below the bottom of the conduction band.

In the title compound, {[Zn2(C10H2O8)(C7H6N2)4]·H2O}n, the ZnII atom has a distorted tetra­hedral geometry, defined by two N atoms from two benzimidazole ligands and two O atoms from two benzene-1,2,4,5-tetra­carboxyl­ate (btc) tetra-anions. The complete btc anion is generated by inversion symmetry. The polymeric structure exhibits one-dimensional double chains running along the [100] direction, which further extend into a three-dimensional supra­molecular network by way of π–π stacking involving the benzimidazole rings. A non-coordinated water mol­ecule completes the structure.

A new model for ferromagnetic interaction between high spin molecules is proposed where diaminotriazine dications as spin carrying units are hydrogen bonded to a diamagnetic cyanuric acid molecule as spin coupling unit.

The capillary flow properties of novel engineering thermoplastic phenolphthalein poly(ether ether ketone) (PEK-C) have been investigated using capillary rheometer. The dependence of viscosity on the wall shear rate and temperature were obtained. The entrance effect was calculated and from which the extensional behavior was also estimated. From the extudate swell ratio the principal normal stress were also evaluated. The melt fracture phenomena were checked and discussed.

In the title compound, [Zn2(C10H2O8)(C6H5N3)4]n, the ZnII atom has a distorted tetra­hedral coordination geometry, defined by two N atoms and two carboxyl O atoms from two benzotriazole ligands and a benzene-1,2,4,5-tetra­carboxyl­ate ligand. The structure exhibits one-dimensional double chains running along the [100] direction, which further extend into a three-dimensional supramolecular network by π–π stacking.

LiNi0.5Mn1.5O4 is regarded as a promising cathode material to increase the energy density of lithium-ion batteries due to the high discharge voltage (ca. 4.7 V). However, the interface between the LiNi0.5Mn1.5O4 cathode and the electrolyte is a great concern because of the decomposition of the electrolyte on the cathode surface at high operational potentials. To build a stable and functional protecting layer of Li3PO4 on LiNi0.5Mn1.5O4 to avoid direct contact between the active materials and the electrolyte is the emphasis of this study. Li3PO4-coated LiNi0.5Mn1.5O4 is prepared by a solid-state reaction and noncoated LiNi0.5Mn1.5O4 is prepared by the same method as a control. The materials are fully characterized by XRD, FT-IR, and high-resolution TEM. TEM shows that the Li3PO4 layer (6 nm) is successfully coated on the LiNi0.5Mn1.5O4 primary particles. XRD and FT-IR reveal that the synthesized Li3PO4-coated LiNi0.5Mn1.5O4 has a cubic spinel structure with a space group of Fd3m, whereas noncoated LiNi0.5Mn1.5O4 shows a cubic spinel structure with a space group of P4(3)32. The electrochemical performance of the prepared materials is characterized in half and full cells. Li3PO4-coated LiNi0.5Mn1.5O4 shows dramatically enhanced cycling performance compared with noncoated LiNi0.5Mn1.5O4.

The flow boiling heat transfer characteristics of liquid nitrogen in three U-tubes with different curvature ratios were investigated experimentally. The effects of inlet pressure, heat flux, and curvature ratio on heat transfer characteristic are analyzed. The results indicate that the local heat transfer characteristics change obviously as fluid flows through the return bend, especially in the case of high heat flux. The drying out occurs near the inner wall of the return bend under high heat flux. A parameter Rh (down/up), which is defined as the ratio of heat transfer coefficient between the downstream and upstream section of U-bend, is proposed to evaluate the contributions of the curvature ratio to the heat transfer. It is found that the Rh (down/up) increases with the decrease of the curvature ratios. Furthermore, the experiments results of the average heat transfer coefficient are compared with the calculated results of the empirical correlations.

Mechanisms for the atmospheric degradation reaction of BrCH2O2 + HO2 were investigated using quantum chemistry methods. The result indicates that the dominant product is BrCH2OOH + O2(3Σ). While CH2O + HBr + O3, BrCHO + OH + HO2 and CH2O + Br + HO3 will be competitive to a certain extent in the atmosphere. Meanwhile, the nascent product – BrCH2OOH reacts easily with OH radicals leading to BrCH2O2 again under the atmospheric conditions. Moreover, OH radicals could act as a catalyst in the net reaction of BrCH2OOH → BrCHO + H2O. Thus the proposed product BrCHO + H2O + O2 in the experiment might be generated from the subsequent reaction of BrCH2OOH with extra OH radicals. Comparisons indicate that halogen substitution effect makes minor contributions to the XCH2O2 (X = H, F, Cl and Br) + HO2 reactions in the atmosphere.

The trans-2-chlorovinyldichloroarsine (Lewisite) was produced and handled during WWI and WWII as chemical warfare agents. It was very difficult to explore its chemical characterization by experiments ways. The quantum chemical calculations proved to be a precise and harmless method for the toxicological system. In this paper, the gas phase reaction mechanisms of OH radical with trans-2-chlorovinyldichloroarsine (lewisite) were studied by second-order Moller-Plesset perturbation theory (MP2) method. The geometries of reactants, products, complexes, and transition states were optimized at the MP2/6-311++G(d,p) level. To gain more accurate mechanistic knowledge, the single-point energies were calculated using G3 and CCSD(T) method. This reaction exhibited three mechanisms, namely, direct hydrogen abstraction, direct chlorine abstraction, and addition/elimination. Multichannel Rice-Ramsperger-Kassel-Marcus theory and transition-state theory have been carried out for overall and individual rate constants over a wide range of temperatures and pressures. The computational results indicated that addition/elimination reaction is more favorable than direct hydrogen abstraction and direct chlorine abstraction. The major products for the total reaction are AsCl2 and CHClCH2O generated via C(2)-addition/elimination.

Environmental context Nitrous acid is an important atmospheric trace gas, but the sources and the chemical mechanisms of its production are not well understood. This study explores the effects of ammonia and water on the hydrolysis of nitrogen dioxide and nitrous acid production. The calculated results show that ammonia is more effective than water in promoting the hydrolysis reaction of nitrogen dioxide. Abstract The effects of ammonia and water molecules on the hydrolysis of nitrogen dioxide as well as product accumulation are investigated by theoretical calculations of three series of the molecular clusters 2NO2–mH2O (m=1–3), 2NO2–mH2O–NH3 (m=1, 2) and 2NO2–mH2O–2NH3 (m=1, 2). The gas-phase reaction 2NO2 + H2O → HONO + HNO3 is thermodynamically unfavourable. The additional water or ammonia in the clusters can not only stabilise the products by forming stable complexes, but also reduce the energy barrier for the reaction. There is a considerable energy barrier for the reaction at the reactant cluster 2NO2–H2O: 11.7kcalmol–1 (1kcalmol–1=4.18kJmol–1). With ammonia and an additional water in the cluster, 2NO2–H2O–NH3, the thermodynamically stable products t-HONO + NH4NO3–H2O can be formed without an energy barrier. With two ammonia molecules, as in the cluster 2NO2–mH2O–2NH3 (m=1, 2), the reaction is barrierless and the product complex NH4NO2–NH4NO3 is further stabilised. The present study, including natural bond orbital analysis on a series of species, shows that ammonia is more effective than water in promoting the hydrolysis reaction of NO2. The product cluster NH4NO2–NH4NO3 resembles an alternating layered structure containing the ion units NH4+NO2– and NH4+NO3–. The decomposition processes of NH4NO2–NH4NO3 and its monohydrate are all spontaneous and endothermic.

The carbazole-endcapped host molecules with tailoring different heteroaryl core and meta-position linkage mode have great potential on phosphorescent organic light-emitting diodes. To provide a profound view on structure–property relationships, new linear-shaped counterparts have been designed based on the existing molecular composition and the linkage at para-position (p-type molecules). A series of studies about the influence of the linkage mode on optical and electronic properties of these carbazole derivatives have carried out via density functional theory and time-dependent density functional theory calculations. The geometric and the electronic structure of these molecules in the ground states, ions states, and lowest triplet states have been calculated especially focusing on the analysis of highest occupied molecular orbitals, lowest unoccupied molecular orbitals, energy gaps, triplet energies, ionization potentials, electron affinities, reorganization energies, triplet exciton-formation fraction, and absorption spectra. These optoelectronic properties can be effectively tuned by the chemical modifications of different linkage pattern. The good coordination between our calculated results and the available experimental data has been observed. The study reveals that the designed p-type molecules show great promise as new high-performance red host materials with large triplet energy, narrow energy gap, good electron and hole-transport properties, and high triplet exciton-formation fraction.

Stimulated by the preparation and characterization of the isolated pentagon rule (IPR) violating chlorofullerene: C(60)Cl(8) (Nat. Mater. 2008, 7, 790-794), we have performed a systematic investigation on the structural stabilities, electronic and optical properties of the IPR-violating C(60)X(8) (X = H, F, and Cl) fullerene compounds via density functional theory. The large energy gaps between the highest occupied and the lowest unoccupied molecular orbitals provide a clear indication of high chemical stabilities of C(60)X(8) derivatives, and moreover, the C(60)X(8) molecules present great aromatic character with the negative nucleus independent chemical shift values. In the addition reactions of C(60) (C(2v)) + 4X(2) → C(60)X(8), a series of exothermic processes are involved, with high reaction energies ranging from -71.97 to -233.16 kcal mol(-1). An investigation on the electronic property shows that C(60)F(8) and C(60)Cl(8) could be excellent electron acceptors as a consequence of large vertical electron affinities. The density of state analysis suggests that the frontier molecular orbitals of C(60)X(8) are mainly from the carbon orbitals of two separate annulene subunits, and the influence from X atoms is secondary. In addition, the ultraviolet-visible spectra and second-order hyperpolarizabilities of C(60)X(8) are calculated by means of time-dependent density functional theory and a finite field approach, respectively. Both the average static linear polarizabilityαand second-order hyperpolarizabilityγof C(60)X(8) increase greatly compared to those of C(60).

A dual-level direct dynamic method is employed to study the reaction mechanism of hydroxyl radical with (CH(3))(3)COOH and (CH(3))(2)CHOOH. Eight hydrogen abstraction channels are found for title reactions. The energy paths are optimized at the BHH-HLYP/6-311G(d,p) level, and the energy profiles are further refined by interpolated single-point energies method at the CCSD(T) and QCISD(T) theories. Rate coefficients for the reactions of the OH with (CH(3))(3)COOH/(CH(3))(2)CHOOH are computed by the canonical variational transition-state theory with the small-curvature tunneling correction between 200 and 2000 K. The Arrhenius expressions k(1) (T) = 1.49 × 10(-26) T(4.71) exp(1981.92/T) and k(2) (T) = 1.58 × 10(-20) T(3.32) exp(210.59/T) over 200-2000 K are obtained.

The triplet potential energy surface of the O(3P) + CH3CFCH2 reaction has been investigated at the BMC-CCSD//MP2/6-311++G(d,p) level. Multichannel RRKM theory and transition state theory are employed to calculate the rate constants over a wide range of temperatures and pressures. The total rate constants show positive temperature dependence and pressure independence. At pressure of 10 Torr with He as bath gas, the addition/elimination on triplet potential energy surface is a dominant pathway. Major predicted end products are CH3CFCHO (I) and H at the temperatures between 200 and 3,000 K; the direct hydrogen abstraction leading to OH + CH2CFCH2(I) plays an important role at higher temperatures. The calculated overall rate constants are in good agreement with the available experimental data.

The mechanism and kinetics of the reaction of acrylonitrile (CH(2)=CHCN) with hydroxyl (OH) has been investigated theoretically. This reaction is revealed to be one of the most significant loss processes of acrylonitrile. BHandHLYP and M05-2X methods are employed to obtain initial geometries. The reaction mechanism conforms that OH addition to C[double bond, length as m-dash]C double bond or C atom of -CN group to form the chemically activated adducts, 1-IM1(HOCH(2)=CHCN), 2-IM1(CH(2)=HOCHCN), and 3-IM1(CH(2)=CHCOHN) via low barriers, and direct hydrogen abstraction paths may also occur. Temperature- and pressure-dependent rate constants have been evaluated using the Rice-Ramsperger-Kassel-Marcus theory. The calculated rate constants are in good agreement with the experimental data. At atmospheric pressure with N(2) as bath gas, 1-IM1(OHCH(2)=CHCN) formed by collisional stabilization is the major product in the temperature range of 200-1200 K. The production of CH(2)CCN and CHCHCN via hydrogen abstractions becomes dominant at high temperatures (1200-3000 K).

Molecules with D-π-A structures are drawing increased attention for applications in organic electronic devices due to their distinct optoelectronic properties. A study of a new series of bipolar fluorophores that have been chemically modified for use as highly efficient nondoped blue organic light-emitting diodes (OLEDs) has been carried out based on existing molecular structures and a literature survey. The aim of this study is to provide a profound interpretation of the optical and electronic properties and the structure–property relationships of a series of new bipolar fluorophores. The study also aims to predict the photophysical and optoelectronic properties of the new fluorophores. The density functional theory (DFT) has been confirmed as reliable, especially in predicting the properties of unknown products. The geometry and the electronic structure of these molecules in the ground state were studied with DFT and ab initio HF, whereas the lowest singlet excited-state geometries were optimized by ab initio singlet configuration interaction (CIS). The absorption and emission spectra, both in the gas phase and in THF, and the lowest singlet excited energies were calculated by employing the time-dependent density functional theory (TDDFT) and the polarizable continuum model (PCM). To precisely predict the charge-transporting and charge-confining properties of the new fluorophores, three-layered devices have been simulated. The results show that the molecular geometries, HOMOs, LUMOs, energy gaps, ionization potentials (IP), electron affinities (EA), radiative lifetimes ( τ ), absorption and emission spectra are all tuned by chemical modifications with different π-conjugated bridges. The results also show that these molecular materials could be used as bipolar light-emitting materials for blue and deep-blue OLEDs.

The doping mechanism and electronic properties of Clo−4 in polyacene are studied by means of quantum chemistry CNDO/2 method. Stable adsorption sites of Clo−4 are found over the midpoint of chemical bonds C=C and C-C of polycaene molecule, and in the former site larger adsorption energy is given rise to. Clo−4 is also easy to migrate toward C=C amd C-C when it is adsorbed on the other sites. It is demonstrated by the comparison of energy band structures that the doped system has higher conductivity if ClO−4 is adsorbed at the hole site or bridge site of C=C.

The geometries of the three structures of poly-(3-methylpyrrole-4-carboxylic acid) (PMPC), reduced (a), half-oxidized (b) and oxidized PMPC (c), have been optimized by means of MNDO program. The electronic and energy band structures of these systems have been studied by means of EHMO-CO method. The self-doping conducting mechanism was explored in terms of the calculational results.

Two-dimentional electronic energy bands of pristine and iodine doped 1,4-cis-polyisoprene (PI) are calculated by semiempirical EHMO-CO method. The results show that the conductivity of iodine doped PI results from the conduction of both parallel and perpendicular to the chain direction; the conductivity of interchain is higher than that of intrachain. I3n− (n

The conductivity and the ratio σ : /σ⊥ of undoped PA are 10−5 s/cm and 100, and AsF5-doped PAs' are 103 s/cm and 10, respectively. We used the EHMO/CO method to calculate the 2-D energy band structures of high oriented undoped and AsF5-doped PA. Using the calculation results we can well explain the change of conductive properties from undoped PA to AsF5-doped PA.

Earlier work demonstrated that either a simple fourth-order polynomial or a pair of Morse functions could be fit with high accuracy to model proton transfers across H-bonds. The work is extended here to a systematic set of angular distortions in the H2O‥H+‥OH2 and H3N‥H+‥NH3 systems. So long as the deformation does not impose a left-right asymmetry into the system, either of these types of functions can reproduce ab initio transfer potentials well. But the Morse potentials are superior in that neither stretches nor bends of the H-bonds cause large variation in the parameters. For those modes of angular distortion which introduce asymmetry into the transfer potential, the ab initio data can be accommodated by permitting small variations in two of the parameters in the Morse functions. © 1993 John Wiley & Sons, Inc.

The mechanisms and kinetics studies of the OH radical with alkyl hydroperoxides CH3OOH and CH3CH2OOH reactions have been carried out theoretically. The geometries and frequencies of all the stationary points are calculated at the UBHandHLYP/6-311G(d,p) level, and the energy profiles are further refined by interpolated single-point energies method at the MC-QCISD level of theory. For two reactions, five H-abstraction channels are found and five products (CH3OO, CH2OOH, CH3CH2OO, CH2CH2OOH, and CH3CHOOH) are produced during the above processes. The rate constants for the CH3OOH/CH3CH2OOH + OH reactions are corrected by canonical variational transition state theory within 250–1500 K, and the small-curvature tunneling is included. The total rate constants are evaluated from the sum of the individual rate constants and the branching ratios are in good agreement with the experimental data. The Arrhenius expressions for the reactions are obtained. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011

The dual-level direct kinetics method has been used to investigate the multichannel reactions of C(2)H(5)I + Cl. Three hydrogen abstraction channels and one displacement process are found for the title reaction. The calculation indicates that the hydrogen abstraction from -CH(2)- group is the dominant reaction channel, and the displacement process may be negligible because of the high barrier. The rate constants for individual reaction channels are calculated by the improved canonical variational transition-state theory with small-curvature tunneling correction over the temperature range of 220-1500 K. Our results show that the tunneling correction plays an important role in the rate constant calculation in the low-temperature range. Agreement between the calculated and experimental data available is good. The Arrhenius expression k(T) = 2.33 x 10(-16) T(1.83) exp(-185.01/T) over a wide temperature range is obtained. Furthermore, the kinetic isotope effects for the reaction C(2)H(5)I + Cl are estimated so as to provide theoretical estimation for future laboratory investigation.

In this paper, we use the semi-empirical Hartree–Fock method introduced within the finite electric field perturbation approach, to calculate the molecular and π-system polarizabilities of trans and cis polyene H(-CH=CH-)nH (n = 3, 4, 5, …, 18). The result is that for a given n, the order of both molecular and π-system polarizabilities of polyene is trans > cis. This result is consistent with the order of experimental values of trans and cis hexatriene. When the n increases from 3 to 18, the contribution of π-system polarizability to the molecular polarizability increases from 45 to 70%. Using these results, we have extrapolated the polarizabilities of both trans and cis polyacetylene. The order is trans > cis. These results and crystal parameters lead to an estimate of the dispersion energies among polyacetylene chains. The result is also Edisp(trans) > Edisp(cis). Keywords: polarizability, polyacetylene, cis/trans, CNDO, dispersion energy.

Two phase flow pattern in pressurized coil has been predicted. The formulae, procedure, general computer program and flow sheet for calculating pressure drop and heat transfer in the coil are presented. The work attempts to provide optimum design method for small medical Dewar and provide a clear understanding of two phase flow heat transfer in the pressurized coil.

A dual-level direct dynamic method is employed to study the reaction mechanisms of CF(3)CHFOCF(3) (HFE-227 mc) with the OH radical and Cl atom. The geometries and frequencies of all the stationary points and the minimum energy paths (MEPs) are calculated at the BH&H-LYP/6-311G(d,p) level, and the energetic information along the MEPs is further refined by MC-QCISD theory. The classical energy profile is corrected by the interpolated single-point energies (ISPE) approach, incorporating the small-curvature tunneling effect (SCT) calculated by the variational transition state theory (VTST). The rate constants are in good agreement with the experimental data and are found to be k(1) = 2.87 x 10(-21)T(2.80) exp(-1328.60/T) and k(2) = 3.26 x 10(-16)T(1.65) exp(-4642.76/T) cm(3) molecule(-1) s(-1) over the temperature range 220-2000 K. The standard enthalpies of formation for the reactant CF(3)CHFOCF(3) and product radical CF(3)CFOCF(3) are evaluated via group-balanced isodesmic reactions, and the corresponding values are -454.06 +/- 0.2 and -402.74 +/- 0.2 kcal/mol, respectively, evaluated by MC-QCISD theory based on the BH&H-LYP/6-311G(d, p) geometries. The theoretical studies provide rate constants of the title reactions and the enthalpies of formation of the species, which are important parameters in determining the atmospheric lifetime and the feasible pathways for the loss of HFE-227 mc.

Stimulated by the recent isolation and characterization of C56Cl10 chlorofullerene (Tan et al., J Am Chem Soc 2008, 130, 15240), we perform a systematic study on the geometrical structures, thermochemistry, and electronic and optical properties of C56X10 (X = H, F, and Cl) on the basis of density functional theory (DFT). Compared with pristine C56, the equatorial carbon atoms in C56X10 are saturated by X atoms and change to sp3 hybridization to release the large local strains. The addition reactions C56 + 5X2 → C56X10 are highly exothermic, and the optimal temperature for synthesizing C56X10 should be ranged between 500 and 1000 K. By combining 10 X atoms at the abutting pentagon vertexes and active sites, C56X10 molecules exhibit large energy gaps between the highest occupied and lowest unoccupied molecular orbitals (from 2.84 to 3.00 eV), showing high chemical stabilities. The C56F10 and C56Cl10 could be excellent electron acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities. The density of states is also calculated, which suggest that the frontier molecular orbitals of C56X10 are mainly from the carbon orbitals of two separate annulene subunits, and the contributions derived from X atoms are secondary. In addition, the ultraviolet–visible spectra and second-order hyperpolarizabilities of C56X10 are calculated by means of time-dependent DFT and finite field approach, respectively. Both the average static linear polarizability 〈α〉 and second-order hyperpolarizability 〈γ〉 of these compounds are larger than those of C60 due to lower symmetric structures and high delocalization of π electron density on the two separate annulene subunits. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2011

The reaction of H radical with C2H5CN has been studied using various quantum chemistry methods. The geometries were optimized at the B3LYP/6-311+G(d,p) and B3LYP/6-311++G(2d,2p) levels. The single-point energies were calculated using G3 and BMC-CCSD methods based on B3LYP/6-311++G(2d,2p) geometries. Four mechanisms were investigated, namely, hydrogen abstraction, C-addition/elimination, N-addition/elimination and substitution. The kinetics of this reaction were studied using the transition state theory and multichannel Rice-Ramsperger-Kassel-Marcus methodologies over a wide temperature range of 200–3000 K. The calculated results indicate that C-addition/elimination channel is the most feasible over the whole temperature range. The deactivation of initial adduct C2H5CHN is dominant at lower temperature with bath gas H2 of 760 Torr; whereas C2H5+HCN is the dominant product at higher temperature. Our calculated rate constants are in good agreement with the available experimental data. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010

A systematic study on the geometrical structures and electronic properties of C(68)X(4) (X=H, F, and Cl) fullerene compounds has been carried out on the basis of density functional theory. In all classical C(68)X(4) isomers with two adjacent pentagons and one quasifullerene isomer [C(s):C(68)(f)] containing a heptagon in the framework, the C(s):0064 isomers are most favorable in energy. The addition reaction energies of C(68)X(4) (C(s):0064) are high exothermic, and C(68)F(4) is more thermodynamically accessible. The C(68)X(4) (C(s):0064) possess strong aromatic character, with nucleus independent chemical shifts ranging from -22.0 to -26.1 ppm. Further investigations on electronic properties indicate that C(68)F(4) and C(68)Cl(4) could be excellent electron-acceptors for potential photonic/photovoltaic applications in consequence of their large vertical electron affinities (3.29 and 3.15 eV, respectively). The Mulliken charge populations and partial density of states are also calculated, which show that decorating C(68) fullerene with various X atoms will cause remarkably different charge distributions in C(68)X(4) (C(s):0064) and affect their electronic properties distinctly. Finally, the infrared spectra of the most stable C(68)X(4) (C(s):0064) molecules are simulated to assist further experimental characterization.

A comparative study using density functional theory (DFT) on the molecular structure, electronic structure and relative properties of 1,3,4-oxadiazole dimers 1,3-bis[2-(4-methylphenyl)-1,3,4-oxadiazol-5-yl]benzene (OXD-X) and its derivatives with alkoxy substituents –O(CH2)n−1CH3 (OXD-An, n = 1, 2) and electron-withdrawing substituents –CN (OXD-C), –CF3 (OXD-TFM), –NO2 (OXD-N) added at meta-substitution in the phenyl ring are presented. The ground state structures of the title complexes are optimized at B3LYP/6-31G level of theory. In addition, the time dependent density functional theory (TDDFT) method is applied to calculate the absorption and emission spectra of the derivatives based on the ground state geometries. Comparing with the alkoxy substituents, the results show that the electron-withdrawing substituents have remarkable influences on the energy levels of the frontier molecular orbitals, the spectra and the transition compositions. Especially, –NO2 group plays the prominent role and the fluorine improves the energy level of LUMO further. The experimental absorption wavelengths for OXD-X, OXD-A3 and OXD-A7 are well reproduced by the TDDFT technique. Moreover the absorption wavelengths and the transition compositions can be effectively adjusted through introducing electro-withdrawing groups in the phenyl ring. The reorganization energies for hole and electron are smaller than that of typical hole and electron transport materials.

It is well known that the aurophilic attraction has great influence on spectra properties. There are certain relationships between spectra and nonlinear optical properties (NLO). Here, XMPH3, (XMPH3)2 (X = F, Cl; M = Au, Ag, and Cu) were taken as the examples to be investigated to study the relationship between NLO and M···M interactions. The NLO properties of XMPH3, (XMPH3)2 (X = F, Cl; M = Au, Ag, and Cu) were carried out with finite field/second-order Moller–Plesset perturbation theory method. The results show that polarizability tensors of dimers (αtot,d) and second-order hyperpolarizability tensors of dimers (γtot,d) are significantly larger than αtot,m and γtot,m of corresponding monomers. It indicates that M…M interaction significantly increases αtot,d and γtot,d values. The analysis of the electronic transition shows that the charge transfer along M…M direction play the key role on increasing αtot,d and γtot,d. On the other hand, the βtot is significantly increased by changing ligands and is slightly influenced by M…M interaction. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010

The reaction of N2H4 with OH has been investigated by quantum chemical methods. The results show that hydrogen abstraction mechanism is more feasible than substitution mechanism thermodynamically. The calculated rate constants agree with the available experimental data. The calculated results show that the variational effect is small at lower temperature region, while it becomes significant at higher temperature region. On the other hand, the small-curvature tunneling effect may play an important role in the temperature range 220−3000 K. Moreover, the calculated rate constants show negative temperature dependence at the temperatures below 500 K, which is in accordance with Vaghjiani's report that slightly negative temperature dependence is found over the temperature range of 258−637 K. The mechanism of the major product (N2H3) with OH has also been investigated theoretically to understand the title reaction thoroughly. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2010

The electronic energy bands of pristine and doped polyphenothiazine (PTL) were calculated by semi-empirical EHMO-CO method. The results showed that solitons were the contributors to the conductivity for undoped PTL; charge solitons or polarons were the most likely charge carrieres for protonic acid doped PTL; polarons were probably the dominant contributors to conductivity for AsF5 doped PTL. The highest conductivity may be achieved by double doping.

The electronic structures of six kinds of methyl substitutional polyacene are studied on the basis of the one-dimensional tight-binding SCF-CO (self consistent field-crystal orbital) method. The calculated results indicate that methyl substitutional polyacene is organic conductor with higher conductivity in pristine state.

To determine the geometries of the most stable hept-C62X2 (X = F, Cl, and Br) isomers, all 967 possible hept-C62F2 isomers have been orderly optimized using AM1, HF/STO-3G, B3LYP/3-21G, and B3LYP/6-31G* methods, and chlorofullerenes and bromofullerenes, which are isostructural with five most stable hept-C62F2 isomers, were regarded as candidates of the most stable isomer, and optimized at the B3LYP/6-31G* level. The results reveal that 2,9- and 9,62-hept-C62X2 (X = F, Cl, and Br) are the two most stable isomers with slight energy difference. The halogenation releases strain energy of hept-C62, and all halogenated fullerenes are more chemically stable than hept-C62 with lower EHOMO and higher ELUMO. All five most stable hept-C62X2 (X = F, Cl, and Br) isomers are energetically favorable, and their thermodynamic stability decreases along with the increase of sizes of addends. Only hept-C62F2 isomers show high thermodynamic stability, and they are potentially synthesized in experiments. 59,62-squ-C62X2 (X = F, Cl, and Br) were computed for comparison, and they are found to be more stable than their heptagon-containing isomers. © 2008 Wiley Periodicals, Inc. J Comput Chem 2008

Mechanisms and kinetics of the NCCO + O 2 reaction have been investigated using the extrapolated full coupled cluster theory with the complete basis set limit (FCC/CBS) and multichannel RRKM theory. Energetically, the most favorable reaction route involves the barrierless addition of the oxygen atom to one of the carbon atoms of NCCO and the subsequent isomerization-decomposition via the four-center intermediate and transition state, leading to the final products NCO and CO 2 . At 298 K, the calculated overall rate constant is strongly pressure-dependent, which is in good agreement with the available experimental values. It is predicted that the high-pressure limit rate constants exhibit negative temperature dependence below 350 K. The dominant products are NCO and CO 2 at low pressures (ca.

We design a way that the anode hosts provide lithium ion in lithium ion battery operation. If the limiting factors of the cathode materials are less, there will be more alternatives for it. It was proven to be successful by two kinds of test cells based on LixCn as anode material, and β-FeOOH or Cr8O21 as cathode materials. Their theoretical capacities are much higher than those present electrode materials. Unlike the lithium secondary batteries with lithium metal foil or lithium alloy as anode, this type of lithium ion batteries with LixCn as anode prohibit dendrite formation during charging-discharge process. The idea of lithium ion sources coming from the anode can come true successfully as a result that steady protecting solution be sought for LixCn.

The interactions of benzene (C6H6), naphthalene (C10H8), and perinaphthene (C13H9) with metal atoms (Li, Ca, and Al) were studied using second-order Møller-Plesset perturbation theory. By analyzing the frontier molecular orbitals, geometric structures, binding energies, and charge transfers, it was found that these metal atoms can bond strongly with C13H9, but can only bond weakly with C6H6 and C10H8. The bonding nature between a metal atom and C13H9 at their ground state depends significantly on the valence orbital of the metal atom and the pi-bonding distribution of the aromatic hydrocarbons. The spindly shaped 3p valence orbital of an Al atom results in the deviation of the adsorption site to the edge of C13H9, whereas the ball-shaped 2s/4s valence orbitals of a Li and a Ca atom facilitate their overlap with the second lowest unoccupied molecular orbital of C13H9. Further, Hartree-Fock and density-functional theory methods were demonstrated generally to be unreliable in describing the interactions of metal atoms with these pi systems.

Publisher Summary This chapter investigates the use of the two-fluid model of two-phase flow, which is included in a commercial computational fluid dynamics (CFD) code, to numerically predict the boiling flows of cryogenic liquid in a vertical tube. Important information, including heat transfer coefficient, void fraction, and pressure loss was obtained. Comparison between the simulated heat transfer coefficients and the experimental values available in the literature showed an encouraging agreement. Since other parameters such as the void fraction and the pressure loss, which are not available in the related literature, are essentially related to the heat transfer coefficients, the validity of them therefore could be rationally explained according to that of the heat transfer coefficients. It also can be concluded that CFD prediction can offer plenty of important information which is difficult to be measured in experiments, therefore it offers an effective and powerful method for cryogenic engineering designing and studies.

Phenolic resin-based nanoscopic carbonaceous materials have been prepared by doping different proportions of ZnCl2 into phenolic resin (PR) precursor at various heat-treatment temperatures and characterized by means of Brunner-Emmett-Teller method (BET), X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy analyses. The results show that as the ratio of PR to ZnCl2 is 1:3, the average size of grains and apertures are about from 40 to 60 nm and 3.86 nm, respectively, reaching nanometer level. When this material is used as electrode material of lithium ion battery, the reversible capacity the battery could be kept at 370 mA•h•g−1 after 10 charge/discharge cycles.

Poly (vinyl alcohol) (PVA)/H3PMo12O40ultra-fine fiber aggregates contained differential weight percentage of H3PMo12O40 to PVA (20, 50 and 80 wt.%, respectively) have been successfully prepared by electrospinning technique. By means of IR spectrum, wide-angle X-ray diffraction, and scanning electron microscope (SEM) techniques, the fiber aggregates were characterized. The result from scanning electron microscopy (SEM) showed that the average diameter of the fibers was between 240-900 nm. The photochromic behavior of the fiber aggregates was investigated by means of IR, UV-Vis spectra and electron spin resonance (ESR). The results showed that the Mo atom of H3PMo12O40 was reduced via one-electron step and the PVA was oxidized to unsaturated ketone after the PVA/H3PMo12O40 fiber aggregates was irradiated under UV light. The color of the fiber aggregates changed from white to blue under ultraviolet irradiation and the photochromism of the fiber aggregates was reversible in air condition.

The photoluminescent properties of an optical microcavity formed by a single layer of PPV film sandwiched between a quarter-wavelength distributed Bragg reflector and a metal Ag reflector was studied. The significant microcavity effect was observed. (1) The PL emission spectrum of PPV film is a wide band spectrum with two peaks at 510 nm and 550 nm, respectively. The PL emission spectrum of the microcavity shows 2 peaks, which is at 564 nm and 599 nm, respectively. The FWHM of the narrowed emission spectrum is 7 nm. The PL emission intensity of the microcavity at the resonant mode of 564 nm is enhanced by 19 times. (2) It was found that the peak of the microcavity is blue-shifted with the decreasing of emission intensity obviously when the detection angle is increased. We consider that this is a novel phenomenon and worth investigating further.

The organometallic complexes of transition metal M = Cu(I), Ag(I), Au(I) with d10 electronic configuration have interesting optical, electronic and magnetic properties. It is possible to prepare the high functional organometallic polymer materials by coordinating π-conjugated organic molecules with d10 metals. According to the experimental structures, the model polymers [M-C-C(N)]n are built up and quantum chemistry methods are used to calculate their properties. It is indicated from theoretical analysis that the organometallic polymers would have comparable conductivity when interactions exist between metals and π electrons of different chains.

A detailed theoretical survey on the potential energy surface for the CN + C4H2 reaction is carried out at the QCISD(T)/6-311+G(d,p)//B3LYP/6-311+G(d,p) level. The geometries, vibrational frequenci...

In the title compound, {[Cu(C17H17FN3O3)2]·2H2O}n, the CuII atom exists in a distorted trans-CuN2O4 octa­hedral geometry that is defined by two monodentate N-bonded and two bidentate O,O-bonded 1-cyclo­propyl-6-fluoro-4-oxo-7-(1-piperazinyl)-1,4-dihydro­quinoline-3-carboxylate (cf) mono­anions. The extended two-dimensional structure is a rectangular grid. The Cu atom lies on a centre of inversion.